Conventionally, there has been known a substrate processing apparatus that unloads substrates in sequence from a cassette accommodating multiple substrates, and then, performs a process thereon.
By way of example, Patent Document 1 describes a substrate processing apparatus configured to specify an accommodation position for each substrate accommodated in a cassette by using a detection unit such as a reflective sensor or the like, unload a substrate from the same cassette according to a specified accommodation position, and return the unloaded substrate to the same cassette.
Patent Document 1: Japanese Patent Laid-open Publication No. H11-145244
However, if the unloaded substrate is not returned to the original cassette but returned to a different cassette, it is difficult to find out an accommodation position in the different cassette by using the above-described technique. For this reason, in this case, the substrate is accommodated according to a target accommodation position previously stored.
However, by way of example, if the cassette is not appropriately mounted on a mounting table or is slightly inclined, an actual accommodation position deviates from the target accommodation position previously stored. Therefore, the substrate may not be appropriately accommodated in the cassette.